Daily Fit News: April 17

A new study looks at how training on an empty stomach impacts fat loss.

Every athlete knows that education is a crucial part of performance. Sport and exercise research, insight from top trainers, science, and technology help you to better understand your body so you can craft a healthier lifestyle, workouts, and recovery plan.

In our daily news series, Matt Berenc, director of education at the Equinox Fitness Training Institute, addresses some of the latest fitness research and news stories.

Today's topic: Should you eat before a workout? The Science: A study from the American Physiological Society looked at the impact of fasted exercise on body fat. The results: When exercising (up to a certain intensity) on an empty stomach, there was a great expression of genes that indicated fat was used as the primary energy source. “This means that more of the calories used to “fuel” the activity came from fat,” explains Berenc. This could mean that fasted workouts help you to burn a higher percentage of fat than non-fasted ones.

EQX Expert Insight: “While this sounds great, the results shouldn’t be taken as a directive to do all training fasted,” warns Berenc. First, consider the type of workout you’re planning. “The participants in the study trained at 60 percent of their VO2 max which is a relatively low intensity that is already supported more by fat oxidation than carbohydrate,” says Berenc. “As the intensity increases, as may be the case with exercises like sprint intervals, you may want some carbs in your system as a ready fuel source.” That’s because during this type of workout, the body is more anaerobic and the dominant fuel source shifts to glycogen. “If you don’t have much to pull from, your performance may decline,” says Berenc. Plus, even though high-intensity workouts use more carbs as the preferred fuel, you are also using more calories overall so you are still utilizing fat at a lower percentage. Second: “Consider whether you feel better with food and what leads to your best performance,” Berenc suggests.

The Bottom Line: If your primary goal is to perform at the highest level possible and you're doing a high-intensity workout, you're better off eating a pre-workout snack. If your goals are focused more around body fat percentage or weight loss, fasted workouts could be a helpful tool. Still: “If you want to give fasted exercise a try, prioritize it for the days that you do lower-intensity training (such as longer runs or a lighter lifting day) and progress from there. Once you build a comfort level at low intensity you can try it at a higher one, being mindful of how you feel and how your body responds.”